Glycobiology Advance Access originally published online on April 24, 2009
Glycobiology 2009 19(8):834-840; doi:10.1093/glycob/cwp061
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Communication |
Genetic analysis of glucosidase II β-subunit in trimming of high-mannose-type glycans
4 RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
5 Department of Biotechnology, University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
1 To whom correspondence should be addressed: Tel: +81-48-467-9430; Fax: +81-48-467-4680; e-mail: yukito{at}riken.jp; Tel: +81-48-467-9434; Fax: +81-48-467-4680; e-mail: atwata{at}riken.jp
Received on September 29, 2008; revised on March 24, 2009; accepted on April 18, 2009
Glucosidase II (G-II) is a glycoprotein-processing enzyme that successively cleaves two
1,3-linked glucose residues from N-linked oligosaccharides in the endoplasmic reticulum. G-II is a heterodimer whose
-subunit contains a glycosidase active site, but the function(s) of the β-subunit remain poorly defined. We report here an in vivo enzymatic analysis using gene disruptants lacking either the G-II
- or β-subunit in the filamentous fungus Aspergillus oryzae. Using synthetic oligosaccharides as probes, G-II activity of the membranous fraction of the gene disruptants was investigated. The fraction lacking the β-subunit retained hydrolytic activity toward p-nitrophenyl
-D-glucopyranoside but was inactive toward both Glc2Man9GlcNAc2 and Glc1Man9GlcNAc2. When the fraction containing the β-subunit was added to the one including the
-subunit, the glucosidase activity was restored. These results suggested that the β-subunit confers the substrate specificity toward di- and monoglucosylated glycans on the glucose-trimming activity of the
-subunit.
Key words: glucosidase II / glycoprotein / oligosaccharide / quality control / Aspergillus oryzae
2 Present address: Department of Materials and Life Science, Seikei University, Musahino, Tokyo 180-8633, Japan.
3 Present address: Department of Chemistry and Chemical Biology, Gunma University, Kiryu 1376-8515, Japan.